Physics perspective of environment

What is energy?

Work (Moving an object) An object in motion Field with an object (e.g. An object put at

higher place) Heat Light

Etc.

Making energy

Making heat by burning oils or coals, etc. Utilizing steam or combustion to create a

physical force Using the force to create electricity Utilizing motions in nature to create electricity Using chemical reactions to create electricity Utilizing quantum reactions to create electricity Using nuclear reactions to create heat

Engine system

1. Intake air and vaporized fuel

2. Compress the air-fuel mixture

3. Ignite the gas

4. Exhaust fumes

To be repeated

Energy cycle system(General concept of engine)

Fuel (Energy sources)

Work / Motion

Intake Exhaust

Energy as a different form

Rotating turbines / crankshaft, etc.

Ecology and energy circulation

Fuel (Energy sources)

Work / Motion

Work / Motion

Work / Motion

Fuel (Energy sources)

Fuel (Energy sources)

Bio-system A

Bio-system B

Bio-system C

Introduction to thermodynamics

The zeroth law Thermal equilibrium and principle of thermometer

The first law Energy conservation

The second law Entropy

The third law Infinite processes to reach absolute zero degree

Zeroth law of thermodynamics

Systems A and B are thermal equilibrium with system C.

Namely, A and B are equilibrium with each other.

This process defines temperature.

Thermal equilibrium

Thermal equilibrium is not uniformity of heat, but there is not heat flows between systems.

80 degrees

40 degrees

60 degrees

60 degrees

The heat flows from higher to lower temperatures.

The heat flow is diminished and the temperature is stabilized:

Thermal equilibrium

Latent heat 1

When a substance transforms into a different phase, the heat flows between the phases without change of the temperature.

The heat that plays this role is known as latent heat.

Latent heat 2

When ice melts, the heat is absorbed by 80 cal per gram.That is why ice can keep things refrigerated.

When water is vaporized, the heat radiates 540 cal per gram.When sweat dries out, the surface of your

skin is significantly cooled down.

First law of thermodynamics

The internal energy of a system transforms into heat flows.

As a system, the internal energy and heat flow are conserved.

Q1 Q2

QT

|QT – Q1| = |Q2 – QT|

Second law of thermodynamics

In an isolated system, the entropy cannot decrease. Energy and substances are diffused.

The work done by heat cannot generate the same amount of internal energy.

Entropy 1

Entropy id defined as the change of the heat energy divided by the absolute temperature.

The process of heat flow entails the increase of entropy

The entropy after the heat flow is larger.

T

QS

80 degrees

40 degrees

T1T2 <

Q2

T2

Q1

T1

<

Entropy 2

When vapor becomes water by cooling, it looks like the entropy decreases.

This is because it is an open system. In terms of the larger system, the entropy increases by the heat radiation.

Vapor

Water

absorption

radiation

Third law of thermodynamics

As the temperature approaches zero, the entropy also approaches zero at thermodynamic equilibrium.

In principle, it is impossible to reach absolute zero.

Steam engines

This was started from the transformation of energy sources. [Wood Coal]

People needed innovation of technology to utilize coals effectively.

T. Savery, T. Newcomen, and J. Watt developed steam engines with energy from coals. [The end of 17 to the middle of 18 centuries]

Newcomen’s engine

1. Burn the coals.

2. Boil the water.

3. The steam raise the pressure of the cylinder to lift the piston.

4. Feed water into the cylinder.

5. Then it pulls down the piston by lowering pressure.

water

Water feeding drainage

piston

cylinder

Watt’s engine

1. Burn the coals.2. Boil the water.3. The steam raise the

pressure of the cylinder to lift the piston.

4. The steam goes down into the condenser and it is cooled down to become water.

5. Then it pulls down the piston by lowering pressure.

water

piston

cooling water

cylinder

cond

ense

r

Work and energy

Work = force distance Kinetic energy = 1/2massspeed2

Gravitational potential energy = massgrav.accel.height

You can find other energy, such as wind, water flows, chemical reactions, etc. These are exchangeable each other.

Energy Work

First law of thermodynamics revisited (Energy conservation) In a system, sum of all the work and

energy is constant. They compensate each other; for

example, more force with less distance, and less force with more distance to move an object.

Without having energy from outside, the system cannot continue to work.

Entropy and work Entropy increases at the direction of

the thermal processes. Work capability can be associated with

the entropy.Energy sources

Work / Motion

Intake Exhaust

Energy / substances as a

different form

Lower entropy

Increasing entropy

Higher entropy

Large capability to work

Small capability to work

Heat as energy

The heat created from electricity is: Q=RI2t where Q, R, I and t are heat, resistance, current and time.

Heat itself is energy: E = kT where k and T are Boltzmann const. and temperature.

1 calorie = 4.19 joules

Carnot cycle 1 The low grade

heat source plays an important role.

All the given heat cannot be used only for the work because the engine is stopped.

Part of the given heat is absorbed into the law grade heat source.

High grade heat source

Low grade heat source

The heat source gives heat to engine.

The inside engine is expanded.

The internal energy flows into the lower

heat source.

The inside engine shrinks.

Carnot cycle 2

This is a reversible system. (repeatable)

The efficiency is given only by T0 and T1.

This system includes the direction of the heat flow.

Thermal system

Work

High grade heat Low grade heat

T1 T0

1

01fficiencyT

TTe

Human-activity system as an engine

*Petroleum *Natural gas

*Metals*Chemical

*Water*Other

substances

*Work / Motion*Products*Electricity

Intake Exhaust

*Residue*Exhaust gas

*Contaminated water

Excess of each process may cause problems…

Depletion of natural resourcesDestroying ecology

Waste disposalproblems

PollutionsDestroying ecology

Human activity and environmental structure Natural resources will be depleted when human

consumption is more than the quantity that nature can produce.

Other biological systems play very important roles to keep various equilibria on the earth.

Environments need to have margins to neutralize exhausted products to manage entire ecology.

Water as an important factor in environment 1 Water is harder to be heated up and

harder to be cooled down. (= high specific heat: 4186 J/kg K)

This provides a stable environment on the earth.

Water as an important factor in environment 2

Water vaporization

Heat radiation

Rain fall as cooled down

vapor

The vaporized waterbecomes lighter to goup. Then, it gets cooledthere and falls as rain orsnow.

Due to the latent heat andradiation, this processRemove excess heat fromthe earth.

Bio-system and its cycle

The system is based upon sun shine and water. Plants produce carbohydrates (sugars) to feed

animals. Animals’ excretory substances are degraded by

bacteria. The substances degraded by bacteria are used

for plants.

This process repeats.

Heat death of the universe 1

If the entropy keeps on increasing, every system will become equilibrium, which is called heat death.

However, an open system exchanges lower and higher entropies.

Entropy keeps increasing in a closed system.

Heat death of the universe 2 In the universe, the entropies flow as in the

structure:

Environmental activities (engines)

The direction of lower

entropies

The direction of higher entropies

Universe

Ecological systems 1

Biological creatures inhabit 10 km (6.21 miles) from the surface of the earth.

Plants produce carbohydrates by photosynthesis.

Animals consume them and excrete as in a different substances.

Bacteria and fungi biodegrade the substances and carcasses for plants.

Ecological systems 2 Bacteria play an important role for the cycle.

Detritus(carcasses and dead

leaves, etc.)

Plants(producing

carbohydrates and proteins)

Bacteria(biodegrading

detritus)

Animals(consuming

plants and other animals)

Organic substances

Inorganic substances

especially for the circulation of nitrate

Ecological systems 3

Bacteria biodegrade carbons and nitrides in detritus into CO2 (carbon dioxide), NH4

+ (ammonium ion), and NO3

- (nitrate ion). Amount of CO2 crated by bacteria is

exactly the same amount consumed by plants.

One gram of soil contains about 1 billion of bacteria (1 million kinds).*

* Computational improvements reveal great bacterial diversity and high metal toxicity in soil. J. Gans, et al. Science, 309, 1387-1390 (2005)

Photosynthesis 1

A simple description of photosynthesis:

Breathing: CH2O + O2 CO2 + H2O

Photosynthesis: CO2 + H2O CH2O + O2

Inorganic substances

WaterInsects fungi

bacteria

CO2

O2

CH2O

Sun light

CH2O is the productfrom photosynthesis.

Photosynthesis 2

The carbohydrate produced by photosynthesis is glucose, C6H12O6.

6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O

Many of glucose get bonded to become starch.

Starch is multiple glucose missing water: (C6H10O5)n

Photosynthesis 3

The entropy of carbon atoms seems decreased by photosynthesis, but the entropy of the larger system is surely increasing.

How? Remember that vaporization of water

makes the entropy increased.

Photosynthesis 4

The actual chemical reaction of photosynthesis is:

6CO2+6H2O+6H2O C6H12O6+6O2+6H2O

The H2O of right hand side radiates heat due to the latent heat. (The increase of entropy)

for photo-synthesis

liquid vapor

Entropy and photosynthesis

To produce glucose by photosynthesis, it needs sufficient water not only for the chemical reaction but also for the “exit” of entropy.

It is said that the imbalance of the entropy-circulation system may cause desertification or other malfunctioning of plant systems.

Water on the earth 1

Specific gravity (S.G.) In general, most of S.G. of substances become

larger (i.e. heavier) when they are refrigerated, but water is different.

Water has S.G., 1.0 when it is at 4 degrees of Celsius. (the heaviest)

Temperature of water, Tw. Tw=0 S.G.=0.999; Tw=50 S.G.=0.988; Tw=100 S.G.=0.958.

The S.G. of ice is 0.917.

Water on the earth 2

The S.G. of water does not depend on the temperatures significantly.

The S.G. of ice is smaller than the liquid phase of water; therefore, the ice can float.

This makes water circulate faster and more easily; thus, it has generated variety of biological species.